A federal grand jury has begun a criminal investigation into last month’s chemical spill in West Virginia, looking into Freedom Industries and West Virginia American Water Company.

According to CNN, subpoenas have been issued for the investigation, which started soon after a holding tank owned by Freedom Industries spilled about 10,000 gallons of crude MCHM and PPH into the Elk River on January 9. United States Attorney Booth Goodwin said on January 10 that his office had “opened an investigation into the circumstances surrounding the release,” and the grand jury’s actions marks steps forward in that case.

Though water bans have been lifted in West Virginia, many residents are still hesitant to drink and use their water — caution that was underscored on Tuesday, when an independent water test initiated by CNN found that there are still trace quantities of MCHM in untreated river water and tap water at two locations in Charleston. The CDC has maintained that levels of crude MCHM below 1 part per million are safe — however, questions remain about whether that threshold is truly safe.

“The water ban has been lifted, but too many west Virginians are left wondering if their water is really safe,” West Virginia Secretary of State Natalie Tennant said during a Senate hearing on the spill Tuesday.

Tennant said people she’s talked to in West Virginia are melting down snow in order to give their children baths. They don’t trust reports of safe water, she said, because there’s so little information on the safety of the chemical. Just last week, news broke that crude MCHM can break down into formaldehyde, which can cause cancer.

During the hearing, put on by the Senate Committee on Environment and Public Works, federal lawmakers called for more regulation in West Virginia as an attempt to prevent spills like this from happening in the future.

“Americans have a right to expect, when they turn their tap on, the water they get is safe,” Sen. Ben Cardin, (D-MD) said at the hearing. “Our laws are just not strong enough to deal with the current situation.”

Lawmakers also expressed their support for a bill from Sen. Joe Manchin (D-W.V.), which would require states to inspect chemical facilities that pose a threat to water sources every three years.